Kv2.1 channel subunits underlie delayed rectifier potassium currents that are expressed in neurons throughout the mammalian CNS. We used confocal and electron microscopy to analyze the subcellular localization of these channels in a variety of rat spinal cord neurons, including motoneurons (MNs), interneurons, and dorsal spinocerebellar tract (DSCT) cells, using a commercially available monoclonal antibody against Kv2.1 (Upstate). Kv2.1 immunoreactivity appeared as distinct surface membrane clusters in somatic and proximal dendritic regions. Clusters varied in size and complexity depending on neuron type, with the largest clusters seen on MNs. Quantitative analysis of Kv2.1 channel clusters (n=225 \u27en face\u27 clusters) on MNs revealed a bimodal size distribution including small
